1. Technical Field
The present invention relates to developing devices, image forming apparatuses, image forming systems, and methods for assembling developer supplying rollers.
2. Related Art
(1) Image forming apparatuses such as laser beam printers are well known in the art. Such image forming apparatuses are provided with, for example, an image bearing member for bearing a latent image, and a developing device for developing the latent image borne on the image bearing member with a developer. When the image forming apparatus receives image signals etc. from an external device such as a host computer, it positions the developing device at a developing position which is in opposition to the image bearing member, develops the latent image borne on the image bearing member with the developer contained in the developing device to form a developer image, and transfers the developer image onto a medium to ultimately form an image on the medium.
The developing device of the above-mentioned type is provided with a housing having an opening and adapted to contain a developer, and a developer bearing roller arranged facing the opening and adapted to bear the developer. The developer borne by the developer bearing roller is used for developing the latent image borne by the image bearing member. Further, in order to prevent the developer from spilling from a containing body, the developing device is provided with a first seal member that abuts against the developer bearing roller along the axial direction of the developer bearing roller, and a second seal member that abuts against the end, in the axial direction, of the developer bearing roller along the circumferential direction thereof.
Further, from the viewpoint of preventing the developer from spilling, it is preferable to make the first seal member abut against the developer bearing roller appropriately. To do so, the developing device is provided with an urging member arranged along the axial direction of the developer bearing roller and adapted to urge the first seal member toward the developer bearing roller by abutting against the first seal member. Furthermore, from the viewpoint of preventing the developer from spilling, it is also preferable that the second seal member is supported appropriately. To do so, the developing device is provided with a second seal supporting member that supports the end, in the longitudinal direction, of the second seal member, and the second seal supporting member is attached to the housing such that a boundary section between the second seal member and the second seal supporting member faces the housing. (See, for example, JP-A-2003-280371.)
Depending on, for example, the state in which the second seal supporting member is attached to the housing, there are instances in which a gap is formed between the housing and the boundary section of the second seal member and the second seal supporting member. In cases where such a gap exists between the boundary section and the housing, the developer may spill through the gap, since the developer is a fine particle. In view of this, it is necessary to provide a component member for preventing the developer from spilling through this gap. This, however, may lead to an increase in the number of components of the developing device.
(2) Another type of known developing device that performs development using a developer is provided with a developer supplying roller that supplies the developer to a developer bearing member adapted to bear and carry the developer contained in a developer containing body. (See, for example, JP-A-2004-86059.)
The developer supplying roller of such a developing device is provided inside the developer containing body, which contains the developer. At a position outside the developer containing body, a gear adapted to transmit a motive power for rotating the developer supplying roller from a drive source such as a motor, which is provided outside the developing device, is fixed to a shaft element of the developer supplying roller. In order to prevent the gear and the developer supplying roller from relatively shifting in position in the circumferential direction, a pin is inserted into a pin hole provided in the shaft element in its diameter direction, and the gear and the developer supplying roller are fixed by accommodating the pin, which has been inserted in the shaft element, in a pin-accommodating section provided in the gear. More specifically, the gear is fitted, from the outside, onto the developer supplying roller which projects outward from inside the developer containing body, and the gear is moved up to a position which is more toward the developer containing body than the pin hole provided in the shaft element. After inserting the pin into the pin hole, the gear is moved back to a position where the pin fits into the pin-accommodating section provided in the gear. Then, an E-shaped retaining ring, for example, is fitted into a groove, which is provided in the shaft element on the developer-containing-body-side of the gear, to fix the gear in order to prevent the gear from moving in the axial direction.
Such a developing device is used attached to an image forming apparatus that forms images using the developer. Since there is a demand for downsizing of the image forming apparatus, downsizing of the developing device, which is attached to this image forming apparatus, is also desired.
In the above-described developing device, however, in order to fix the gear to the developer supplying roller, it is necessary to first move the gear closer to the developer containing body than the final fixing position where the gear would be positioned after assembly, and then move the gear back to its final fixing position after insertion of the pin into the pin hole. That is, the developing device contains a space that is used only for assembling the gear to the developer supplying roller and that becomes unnecessary when actually using the developing device. Therefore, such a developing device inevitably becomes large in size.
(3) Another example of a known developing device used in laser printers, which are an example of image forming apparatuses, is a developing device for developing latent images formed on a photoconductor, which is an example of an image bearing member. (See, for example, JP-A-2004-86059.) This type of developing device includes: a housing that has an opening and in which a developer is contained; a developing roller, which is an example of a developer bearing roller that bears the developer and that is arranged facing the opening; and a developer supplying roller adapted to supply the developer contained in the housing to the developing roller.
Such a developing device is further provided with a seal member that abuts against the developing roller to prevent the developer from spilling. The seal member and the developing roller are supported by a support member, and the support member is attached to the housing at both ends in the axial direction of the developing roller.
Further, the developing device is provided with an urging member for urging the seal member toward the developing roller. The urging member urges the seal member toward the developing roller with its urging force to make the seal member abut against the developing roller.
In order to prevent the developer from spilling using the seal member of the above-described type, it is necessary to make the abutting pressure of the seal member against the developing roller even.
Incidentally, a pressing force is applied to the developer supplying roller and the developing roller at both ends thereof where they are supported, so that the developer supplying roller and the developing roller are pressed against one another for the developer supplying roller to supply the developer to the developing roller. This pressing force is applied in a direction in which both ends of the developer supplying roller and the developing roller come closer to one another. Therefore, the developer supplying roller and the developing roller deform at their central sections such that they move away from each other. As a result, even when the seal member is arranged such that it exerts its abutting pressure evenly against the developing roller, the abutting pressure at the central section of the developing roller may become different from the other sections.
Further, if, for example, the developing device is inadvertently dropped during shipping, then the support member that is supported at both ends may become deformed due to the shock applied when the device is dropped. In that case, the support member, which is attached to the housing at both ends in the axial direction of the developing roller, will deform most significantly at the central section. As a result, even when the abutting pressure of the seal member against the developing roller is even at the time of manufacturing the device, the abutting pressure of the seal member at the central section of the developing roller may become different from the other sections at the point of attaching the developing device to the image forming apparatus.